Anal cancer arises when skin cells around the anal opening or inside the anal canal lose the ability to control their growth. Most patients with anal cancer delay evaluation and treatment because their symptoms are written off as hemorrhoid problems. Anal cancer is typically detected by an expert anal exam, and verified using a special scope to visually examine and biopsy the lining of the anal canal. Treatment typically requires surgical biopsy followed by radiation and chemotherapy. Most anal cancers are treated effectively without major surgery or need for a colostomy, but, like colorectal cancer, follow-up care to assess the results of treatment and to check for recurrence is very important.